♪ i'll be there for you these five words i swear to you ♪ ♪ when you breathe, i want to be the air for you i'll be there for you ♪ ♪ i'd live and i'd die for you i'll steal the sun from the sky for you ♪ all right. now we want you to meet the superdogs who can smell your blood pressure and save lives. these dogs can actually sense when your pressure is too low and you are about to faint. >> it is hard to believe. we've seen hero dogs before. but these pups actually intervene before there's a problem. abc's ron claiborne has more on these heroic canines. >> reporter: it's a common friendship. a young woman and her dog. shannon tomlinson and her 2-year-old lab, clover. but watch as something ordinary becomes extraordinary.